Individuals with intellectual and developmental disorders (IDD) face complex health problems and experience substantially higher rates of chronic conditions and behavioral health (BH) problems. They also face unique barriers to high quality care such as inadequate knowledge among health professionals of the way biological, psychological, and social factors interact to determine overall health for people with IDD and communication challenges between patients and providers. There is evidence of significant unmet needs in physical and mental health care that disproportionately impact racial and ethnic minorities, including poorer health, as well as lower rates of recommended preventive screenings and vaccinations, dental services, and social services. Compounding these issues is the high reliance among the IDD population on insurance coverage through Medicaid, which provides much lower reimbursement than other payers. Although prior research provides some evidence of differences across racial and ethnic groups, it does not examine the impact and magnitude of specific system and environmental factors that may give rise to such disparities. Current evidence is of limited value for health policy formulation or system intervention design partly due to limitations in datasets and study designs that limit generalizability and do not allow comprehensive examination of care, utilization and outcomes. This project will identify patient, provider, and system-level factors that drive racial/ethnic disparities in adequacy of ambulatory medical and BH services among Medicaid-enrolled adults with intellectual and developmental disorders. It will specifically focus on IDD program services and their effect on patient overall health and wellbeing. We will use multi-year Medicaid claims data to analyze healthcare utilization and outcomes for individuals with IDD who reside in Intermediate Care Facilities, in the community with eligibility for Medicaid-funded IDD program services, and in the community but not eligible for such services. Understanding variations in system-level factors that contribute to gaps in care will help identify and address underlying racial and ethnic disparities in care among individuals with IDD. Analyses by the study team of service use and expenditures for New Jersey Medicaid beneficiaries show that patients with IDD are among the highest cost beneficiaries and make greater use of inpatient hospital and emergency department care. We will address this issue using a range of guideline-based quality metrics for IDD patients in Medicaid, including measures of preventive service use, inpatient and outpatient health outcomes that reflect coordination and continuity of care, follow up rates, and integration between physical and behavioral health care. Study results can provide important policy guidance relating to performance metrics or incentives within Medicaid managed care contracts; lead to guidelines for health professionals offering specific services; promote patient and family education among minority communities; and inform advocacy organizations about issues such as preventive care and recommended timelines for receiving procedures.